This invention relates to a starting motor, and more particularly to improvements in the buffer of a starting motor equipped with planetary reduction gears.
A prior-art device of the specified type has been as shown in FIGS. 1 and 2. Referring to the figures, numeral 1 designates a D.C. motor, and numeral 2 an armature, which has a rotary shaft 3. An output end part of the rotary shaft 3 is formed with a spur gear 4, with which a planetary gear 5 meshes. Shown at numeral 6 is an internal gear which touches internally, and meshes with, the planetary gear 5. The internal gear 6 is snugly fitted in a socket portion 8 of a front bracket 7 along with an intermediate bracket 9 as well as an elastic member 10, and owing to the installation of the D.C. motor 1, they are fastened in pressed engagement by the abutting force of a yoke 11 of the D.C. motor. Numeral 12 indicates a bearing which is snugly fitted on the inner peripheral surface of the planetary gear 5, and which is carried by a supporting pin 13. Shown at numeral 14 is a flange portion which carries the supporting pin 13 by snugly inserting it therein. A rotary output shaft 15 is unitarily fastened on one side of the flange portion 14, and the rotational speed of the rotary shaft 3 of the armature is reduced and transmitted to this rotary output shaft. Numeral 16 indicates a helical spline which is formed in the outer peripheral surface of the rotary output shaft 15, and which is held in spline engagement with a clutch-outer 18 of an overrunning clutch 17. Numeral 19 designates a roller, numeral 20 a clutch-inner, and numeral 21 a pinion which is fastened to the clutch-inner. Numeral 22 denotes a sleeve bearing which is fitted on the inner peripheral surface of the clutch-inner 20 as well as the pinion 21, and which is loosely fitted so as to swing on the rotary shaft 15. Numeral 23 denotes a washer, and numeral 24 a clutch cover which unitarily fastens the various constituent members. Shown at numeral 25 is a washer which is loosely fitted in a recess 26 provided in the outer peripheral surface of the rear part of the clutch-outer 18, and which forms an engagement portion for a shift lever 27. Numeral 28 indicates a stopper, and numeral 29 a ring which fastens this stopper in engagement with a groove 30 of the rotary shaft 15.
The operation of the device having the above construction will now be described. The shift lever 27 is made to move by an electromagnetic switch, not shown. Thus the overrunning clutch 17 is shifted forward on the rotary output shaft 15 until the pinion 21 comes into mesh with a ring gear of an engine, not shown. Subsequently, the D.C. motor 1 is energized, so that the armature 2 generates a turning force. This turning force is transmitted to the armature rotary shaft 3, with the result that the planetary gear 5 is made to rotate through the spur gear 4. The planet any gear 5 performs a planetary motion due to its simultaneous mesh with the internal gear 6. The resultant turning force is transmitted to the flange 14 through the supporting pin 13, and this turning force is transmitted to the ring gear (not shown) of the internal combustion engine through the rotary output shaft 15, helical spline 16, clutch-outer 18, roller 19, clutch-inner 20 and pinion 21, so that the internal combustion engine is started. In addition, when the planetary gear 5 is made to rotate, a reaction against its turning force develops in the internal gear 6, and the turning force is resiliently opposed by the reactive thrust of the elastic member 10. Accordingly, the impace force developing in the planetary reduction gears is absorbed by the action of the elastic member 10, which acts as a buffer.
With the prior art device, however, the elastic member 10 has a plane surface which abuts on the end face of the internal gear 6, and hence, the deformation of the elastic member 10 is not sufficient. This leads to the disadvantages of an unsatisfactory resilient effect, etc.